1. Field of the Invention
The invention relates to a fuel injection system for an internal combustion engine and a control method for an internal combustion engine.
2. Description of Related Art
Some fuel injection systems for internal combustion engines perform micro fuel injection in order to improve exhaust properties. In improving the accuracy of the micro injection, an irregularity may arise in the injection amount of an injector. Bouncing occurring when a needle valve is fully open is one of the factors causing the irregularity of the injection amount of the injector. The effect of the bouncing of the needle valve on the injection accuracy relatively increases as the injection amount decreases. Accordingly, a lower limit attributable to the mechanism factor of the injector is present in the injection amount allowing injection accuracy to be ensured.
Japanese Patent Application Publication No. 2013-181454 proposes a technique for partial lift injection. The partial lift injection is fuel injection that is performed with the length of time that is required for the needle valve to be fully opened being shorter than energizing time for the injector. The partial lift injection allows a very small amount of fuel to be injected without being affected by the bouncing of the needle valve described above.